Using symmetry to control viscoelastic waves in pillar arrays.

Area of Science:

• Fluid dynamics
• Rheology
• Microfluidics

Background:

• Macromolecular solutions exhibit viscoelastic properties, leading to elastic turbulence and large-scale waves instead of chaotic turbulence under certain conditions.
• These waves manifest as cyclic concentration variations in viscoelastic flow, observed in microfluidic pillar arrays with macromolecular DNA.

Purpose of the Study:

• To investigate how altering the symmetry of microfluidic pillars influences the symmetry of large-scale waves in viscoelastic flow.
• To demonstrate control over viscoelastic flow instabilities for applications in transport, sorting, and mixing.

Main Methods:

• Utilizing microfluidic pillar arrays with modified (asymmetric) pillar geometries.
• Investigating viscoelastic fluid flow dynamics, specifically focusing on the onset and characteristics of large-scale waves.
• Analyzing the relationship between pillar symmetry, wave symmetry, and flow resistance.

Main Results:

• Altering pillar symmetry effectively influences the symmetry of emergent large-scale waves in viscoelastic flow.
• Viscoelastic fluctuations can be suppressed for transport/sorting or enhanced for mixing by controlling pillar symmetry.
• The onset of waves, and thus changes in flow resistance, occurs at different Deborah numbers depending on flow direction through asymmetric pillars.

Conclusions:

• Pillar symmetry is a key parameter for controlling wave symmetry and viscoelastic flow behavior in microfluidic devices.
• This control enables tailored applications, from efficient transport and sorting to enhanced mixing.
• The directional dependence of wave onset and flow resistance in asymmetric pillar arrays allows for the development of fluidic diodes.